German Patent Publications DE 39 35 656 A1; DE 41 29 069 A1 and DE 19 546 672 A1 disclose devices for cleaning an airstream. These devices include an endless filter belt running over two rollers arranged in parallel inside of chambers through which the filter belt travels and wherein the filter belt is heated for desorption of noxious and odorous matter. Conventionally it is necessary to simultaneously desorb noxious and odorous matter from the entire volume of the filter before the filter can again be exposed to the air flow to be cleaned for again loading the filter belt with noxious and odorous matter. Simultaneously desorbing the entire filter belt is not efficient. Another drawback is seen in the fact that the quantity of adsorbing medium is limited due to the need for minimizing the pressure loss caused by the airstream passing through the filter belt. Satisfying these conditions becomes more and more difficult the larger the volume of the airstream to be cleaned and/or the larger the loading degree of noxious and odorous matter becomes. Thus, there is room for improvement.
It is further known to use two filters which are exposed to the air to be cleaned alternately. Thus, one filter does the cleaning job while the other filter is being desorbed or vice versa. Such structures require a relatively large structural volume for the two separate filters. Such space is frequently not available, especially in a passenger vehicle for removing noxious and odorous matter from the passenger compartment space, or rather from the air circulating in the passenger compartment.